What are we listening for during break in?

Is it time for a reality check? A few days ago a post was started which asked a question concerning burn in of interconnect cables. The consensus of answers agreed that this was a necessary function with no opposing view. The recommendation that got me thinking was to install the ICs between cd player and preamp and use a test disc for 250 hours. My immediate reaction to that bit of advice was "give me a break." That is roughly equal to listening to 250 cds. Considering the amount of time I spend listening to music, it would take me six months to break in ICs.
I have experienced a sonic change after new speaker break in period so I'm not argueing break in doesn't occur. Whether a sonic difference occurs after ICs break in is another matter.
My question is, what are we listening for when we run our equipment for 250 hours just to break in an IC or modification? I don't mean why listen to music, I mean what sonic difference are we hearing? Is it better, worse, different, What the?